AUTOMOTIVE ACOUSTICS – A UNIQUE AND CHALLENGING ENVIRONMENT.

Music has become an essential part of our daily lives, playing in our homes, offices, gyms, and even cars. 

Our music preferences might stay the same or change slightly over time, but we use different media to listen to it based on our needs and those are really different from each other.  For instance, we might use small headphones at the gym, a dedicated stereo system at home, or a home theater room to enjoy Dolby Atmos. When it comes to our car, we have access to various media options for enjoying music in different ways. However, it’s crucial to select the right components designed for our specific listening environment.  Just as it’s impractical to wear large home speakers on your head instead of headphones, it’s also nonsensical to assume a speaker designed for home acoustics would be suitable for a car’s acoustics.  And I’m not just talking about the physical shapes and sizes of these speakers! 

No matter if you are a car owner, consumer, or a car audio dealer, I strongly advise against judging a speaker’s compatibility with your car and music preferences by simply listening to it in the same way you would for home speakers.  These two environments are different, and a speaker designed for home use won’t necessarily perform well in a car.  It requires a different approach.

LET’S PUT THIS INTO PERSPECTIVE

When comparing the fundamental acoustic elements of headphones or home speakers, it’s clear that most, if not all, are designed for on-axis listening. This means they’re perfectly positioned in front of you, ideally at ear level.  This is true for both headphones and home speakers.  We’re comfortably seated in an ideal position, almost, with the direct and perfect aim of perceiving all musical notes and subtleties.  Our ears, or our listening position, are perfectly aligned in front of these speakers, so the majority of the acoustic flow reaches our ears directly and centrally from the acoustic source. 

For headphones, this is likely the ideal environment. It largely eliminates acoustic coloration, reverberation, and potential wave cancellation due to your listening location. (We don’t have to deal with any room’s acoustic). However, the small size of the earpiece elements and their close proximity to the audio sources introduce design and acoustic rendering limitations.  Unfortunately, perfection is unattainable. 

Home speakers create more immersive acoustic environments, which you can share with others in the same room.  However, this audio package, whether stereo or multi-channel with Dolby Atmos, must account for your room’s acoustics.  The room’s size, frequency absorption, and reflections all affect the listening experience. While this allows you to share enjoyment with people and is more comfortable than headphones, it introduces an additional acoustic challenge.  However, this setup offers more speaker positioning flexibility compared to a car, allowing you to easily place speakers at equal distances and direct the main acoustic beam toward your listening position. 

THE AUTOMOTIVE ACOUSTIC CHALLENGES

In automotive acoustics, the situation is quite different.  Unlike other environments, our listening position as a driver or passenger isn’t optimized for all speakers.  Cabin design elements influence speaker size, shape and positioning, including distance, height, angles, and whether they’re located at the front or rear of the vehicle.  Some speakers project a direct sound beam, while others, like the left front door sill speaker compared to the right door speaker, may not.  Furthermore, direct sound waves from the speakers interact with various reflected waves from the environment and the different materials of the cabin, such as the dashboard, windows, and trims.  As you can see, we’re in a completely different acoustic world. I won’t delve into the more demanding conditions of temperature, humidity, and vibration in the automotive domain, but I’ll focus solely on acoustic comparisons.

Thanks to modern technology, professional installers in the field use digital signal processors (DSPs) to modulate, modify, and adjust various acoustic parameters through audio processing to alleviate those problems.  However, as with anything, it’s always better to start with a solid foundation and ensure quality from the beginning, rather than rushing the work and needing to make corrections later.  After all, a repair will never be as good as a neat job from the start!

NOTHING IS BETTER THAN A SOLID FOUNDATION

In the world of automotive audio, the speaker is a crucial element for delivering high-quality sound.  While it’s the final link in the audio chain, it plays a vital role in converting electrical signals into air movement, essentially acting as a piston that pushes air and creates the sounds you hear.  If a speaker isn’t functioning properly and doesn’t match your acoustic preferences, you’ll notice the difference immediately.  Theoretically, a loudspeaker should reproduce the acoustic source with the highest fidelity.  However, in reality, each speaker series has its own unique acoustic signature, tailored to appeal to specific audiences or musical styles.  Choosing the right speakers that suit YOUR needs is essential, as you’re the one who benefits, not your neighbor!

Locations, Distances, Angles

A closer look at the vehicle’s speakers reveals that the passenger-side speaker is positioned at a more favorable angle for direct sound transmission.  Since high frequencies are more directional than bass, speakers optimized for direct listening create a situation where the driver perceives greater acoustic presence, dynamics, and detail from the right side compared to the left.  Even identical speakers installed the same way can produce a completely different listening experience.  This is undesirable because the singer’s voice and all instruments should remain constant regardless of their position in the music recording. 

Lower or Higher Soundstage

This exercise applies to vertical movements as well.  For example, consider a front speaker system with multiple speakers, like a 6.5-inch speaker at the bottom of the doors and a tweeter higher up, either in the door or the dashboard.  These speakers should be seamlessly integrated and work together to create a single sound source. However, if the frequency transitions aren’t carefully chosen or the filter cutoff intensity isn’t set correctly, it can cause unwanted vertical audio movement depending on the frequencies being played.  For instance, a singer or instrument might sound like it’s coming from knee height, while higher notes seem to be at eye level. 

Acoustic Reflections

Automobiles are certainly the environments with the most acoustic reflections.  The close proximity of the various walls in the passenger compartment, along with their unique angles and textures from different materials, creates secondary waves that are either generated, altered, or partially absorbed. These waves blend with the original sound source, ultimately shaping the final audio experience.  Speaker design and installation can influence this. Some speakers, once installed, produce a dominant main acoustic beam, while others offer indirect listening. For instance, our TS-H150-RA tweeters, specifically designed for certain Toyota RAV4 models, will be perfectly aligned with your ears.  In contrast, the tweeters in our TS-A653FH coaxial speakers, once installed in the bottom of the rear doors of the same vehicle, will provide a different listening experience. 

Quality Automotive Speakers Must Offer;

1. Remarkable acoustic similarity between direct (on axis) and off-axis listening.
2. Acoustic design made for various positioning challenges and varying component distances.
3. Consistent acoustics in harsh automotive environments.
4. Good acoustic performance despite the physical limitations of the environment.
5. A pleasant listening experience that allows you to forget the source and fully enjoy your musical bubble of happiness!

Watch Out for Easy Traps!

A speaker might sound fantastic when you’re in a perfectly positioned, ideal listening environment. However, its acoustic signature can drastically change when you listen at an angle.  A pronounced difference between direct and angled listening will definitely create an acoustic inconsistency in your vehicle.  Remember, you won’t be listening to these speakers in your living room with perfect positioning and angle. You’ll be in your car, facing all the acoustic challenges that entail.  Therefore, aim for acoustic uniformity, which is the foundation for selecting your speakers.

If you don’t have access to a test environment where you can compare speakers during your purchase, research their specifications and carefully examine the different frequency response curves for various listening angles.  These graphs will help you understand how well the speaker maintains its acoustic signature in your car, regardless of whether it’s installed in the right or left door.  Ideally, the left and the right door speakers should offer similar acoustics.

You have the opportunity to listen to various speakers in-store, which is fantastic!  Once you’re there, I recommend listening to different speakers using the same audio source and amplification. The only change should be the speaker itself!  While listening to music, move around instead of standing still in your « X » position.  Remember, the sweet spot in your living room isn’t in your car.  Of course, take the time to listen to these speakers in person, but also try listening to them at different angles to best simulate your car’s position relative to the speaker. For example, if it’s installed in the front left door, you’ll be surprised to find some speakers are more stable than others in these position changes. These more stable speakers are the ones that will typically provide the best foundation for your car’s acoustics. Better similarity among speakers reduces the need for electronic corrections.

I can already see some purists reacting strongly.  However, I invite you to approach this with a grain of salt. While the ideal listening environment is in a car, comparing speakers in the same vehicle would be a lengthy and complex task.  That’s why specialized stores have these displays, allowing the customer to compare different products. 

The challenge with these in-store setups is that they’re also designed to create an appealing visual display within the limited space.  Consequently, many car audio dealers opt for these « walls » of speakers.  It also makes more sense to display eight to ten cubes on a wall than having eight to ten demo cars in front of the store.  I know that the idea of this may sound great for some, but moneywise, this is not a good one!

It’s true that listening to these speakers directly in your car won’t be the same, but it’s the closest you can get.  Position yourself in front of the speaker, but at an angle.  Try to replicate your listening position as closely as possible based on the speaker’s location in your vehicle. For example, you could use an acrylic or ABS plate to simulate the reflection a speaker would have if installed on a rear shelf, reflecting off the rear glass.  Feel free to get creative!

Armed with this information and a few helpful tips, I’m confident you’ll be able to select the automotive loudspeakers that best suit your needs and sound preferences.  You can start your analysis here.

Important Note

These suggestions are designed to help you select the right speakers.  Once you’ve chosen them, if you’re shopping for other components, such as a new source or a new amplifier, it’s best to set aside all these listening setups and select the sweet spot for your listening sessions. This way, you can take advantage of all the acoustic information available to select the right electronic devices for your car audio system. For example, with our newest Dolby Atmos receiver, the Pioneer SPHERA (DMH-WT8000NEX), it’s ideal to listen to it in a car after a mandatory unit calibration.  If you don’t have access to a demo vehicle and listen in a showroom, ensure you’re on the « X » used for in-store calibration, the SPHERA unit is in a small room simulating a car cabin, and you have at least four speakers (RR, RL, FR, FL).  Each setup has its own procedures and requirements. 

On that note, enjoy good music!